The invention described herein relates generally to wind turbines. More specifically, the invention relates to a rotor turning system and method that allows the rotor to turn in a desired rotational direction, but prevents the rotor from turning in an undesired rotational direction.
The process to replace or remove a blade from a wind turbine typically requires an expensive crane and a number of personnel. The crane is used to support the blade, and this same crane at a different time may be used to carry a basket for a worker (often termed a man basket). The worker climbs into the basket and is then raised up to the tip of the blade. A sling (or sock) is physically placed over the blade tip and then slid along the blade. As one may imagine, this is a difficult process in windy conditions. Cranes are very expensive to rent and operate, and the basket can only be used in periods of low wind, due to worker safety concerns. These limitations make blade removal difficult and expensive.
Most wind turbine rotors have three blades, and the rotor is balanced when all three blades are attached. It is relatively easy to rotate a balanced rotor, as the force of gravity (or wind) is usually minimal and manageable, and the rotor can be maintained in a desired position or moved in a desired rotational direction. However, when one or two blades are missing the rotor becomes unbalanced. In unbalanced rotor situations, a danger exists of unwanted rotor movement. Unfortunately, the standard brake caliper is often not designed to hold an unbalanced rotor, nor is it designed to prevent unwanted reverse rotation during unbalanced rotor rotation. An unbalanced rotor often has the force of gravity acting against the intentions of a technician who is trying to move the rotor in a desired rotational direction. If an unbalanced rotor suddenly and unexpectedly reverses direction, a technician inside the nacelle could be exposed to hazardous conditions from moving machine parts.